Gabe Lozano can trace the dramatic success of LockerDome, a darling of St. Louis startups, to a single email in May 2010 — an inbound message from Brian Matthews.

Matthews, transitioning out of his role with Fanball (previously CDM Fantasy Sports), wanted to get back into the tech startup scene and had hoped to catch up on LockerDome’s doings.

Matthews and Lozano met and discussed mostly vision for the young company, which at that point was still focused on managing amateur sports leagues. Three months later, Matthews cut a check — as part of a $750,000 angel investment —to Lozano, became the company’s first director and began what Lozano calls “the most transformational relationship in LockerDome’s history.”

Since Matthews joined as a director, LockerDome has grown from 10,000 users in 2010 to nearly 20 million users today. The sports social media website also has gone on to raise more than $8 million in venture capital, including some from Matthews.

“Brian Matthews ... is a game changer for any company,” Lozano said. “When we look for directors, we look for individuals that can provide impactful feedback, have enough humility to be wrong and champion the right solution, open up new doors, and are practical, honest and responsive. Brian Matthews embodies all of these qualities.”

Now, Matthews sits on the boards of nearly half a dozen local startup companies, including LockerDome, Tunespeak, Systematic Revenue, Hatchbuck and SixThirty. He’s also a general partner at venture capital firm Cultivation Capital, a mentor with Capital Innovators and owner of River City Internet Group.

Matthews said his role with LockerDome has been one of the most exciting jobs he’s ever had.

“The growth is just amazing,” he said. “I’ve had some successful companies in the 90’s that grew fast and it’s just a rush. And that’s what I’m playing this game for, to be able to ride alongside and experience that. That’s why there are serial entrepreneurs, because of that rush during rapid growth. It’s what we strive for.”

Matthews said he focuses on three areas as a director: capital formation, key employee hires and opening doors with business development contacts.

For LockerDome, he’s played a vital role in all three. It was Matthews who introduced Lozano to Keith Cutler, who in May became LockerDome’s senior vice president of strategic partnership. Matthews and Cutler had worked on projects together while Matthews was working for CDM Fantasy Sports and Cutler was with USA Today.

LockerDome’s $6 million Series A funding round in March was led by Cultivation Capital Growth Fund, a venture fund spearheaded, in part, by Matthews.

“On a daily basis companies must make practical and pragmatic decisions to survive. Brian’s practicality allows him to be a tremendous problem solver.”